Had a nice conversation with Craig Boddington at the Houston Safari Club Convention. While discussing the 450/400 3 double he used to own, he told 400NitroExpress and I that, there were serious talks, about Ruger building a #1 in 400 Jeffery. Hornady would load the ammo.
He thought the caliber would be .408 or .409.

I would be nice to see this 400 Jeffery project come to fruition!